I noticed a small amount of water around the front/side of the furnace, so I opened the bottom panel and found rusty water pooled in the bottom. I opened the panel right above that and found the gas burners. I tried to open the panel right above that (right behind the exhaust flue) but I wasn't able to pull it out. I was able to get all the screws off, but the panel wouldn't slide to the side or forward. The lip of the flue, from the furnace, was blocking the panel from coming forward. In any case, is this the panel I should be trying to open in an attempt to check for a drain problem?